Manuel Neuer has been ruled out of Bayern Munich's trip to Schalke on Tuesday and could face a longer spell on the sidelines with a foot injury, according to German newspaper Bild.
On Monday, Bayern announced on their website that Neuer "injured his left foot in training and will miss the match at FC Schalke 04. There will be a final examination on Tuesday."
The 31-year-old Germany goalkeeper missed the run-in to last season with a broken metatarsal in the same foot, suffered during Bayern's Champions League quarterfinal second-leg defeat to Real Madrid.
Neuer returned to action for the club at Werder Bremen last month, but Bild reported that he could now face another months-long spell on the sidelines and expected to undergo surgery.
Former Stuttgart keeper Sven Ulreich is the backup for Neuer, and the 29-year-old has played in 12 competitive matches since joining Bayern in 2015.
He has conceded 13 goals in those games, winning eight, drawing one and losing three, including a 3-2 home defeat to Borussia Dortmund in the DFB Pokal semifinal.
Meanwhile, winger Arjen Robben could also miss the Schalke game as he suffers with an illness.
Robben and Neuer join David Alaba and Juan Bernat -- both have ankle injuries -- on the sidelines, and coach Carlo Ancelotti said he may shake things up further at the Veltins-Arena to keep his players fresh following a strong start to the Bundesliga season.
"We played very well against Mainz and the three points give us even more confidence," he told reporters at his prematch news conference. "We want to follow up that performance against Schalke.
"I believe rotation is important at the moment to keep the players motivated and in good form."